Modular telephone base unit



FIG. 1 is a perspective view, showing my new design;

FIG. 2 is a front elevation thereof; and

FIG. 3 is a rear elevation thereof; and

FIG. 4 is a left side elevational view thereof; and

FIG. 5 is a top plan view, thereof. 

The ornamental design for a modular telephone base unit, as shown. 